Strong-Field Molecular Processes: From Novel Spectroscopies to Lasing in Air

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My research focuses on the quantum description of laser-matter interactions. When strong laser fields interact with molecules, a number of interesting opportunities arise. First, it is possible to use the lasers to control molecular motions. In particular, my research has highlighted methods to control molecular alignment and orientation in space, where laser-based techniques can force all the molecules in a gas to be aligned or point along a single direction. I am also interested in methods to use strong laser fields to probe and investigate the details of molecular motion, both how the nuclei vibrate and rotated, and how the electrons move within the molecules. To this end, my research also involves methods to probe molecular motion where we use the molecules’ own electrons to investigate the molecular motions occurring within the molecules. We first use the laser fields to quickly remove one of the molecule’s electrons, accelerate this electron to high velocities, and then throw the electron back at the parent molecule. By measuring what happens when this electron recollides with the parent molecule, we can gain valuable information about the particular dynamics occurring in the molecule. This method of probing the molecular dynamics can be compared to using a very fast camera flash, where the light of the flash reflects off of the object of interest, and the camera records how the light scatters from the object. In the molecular case, the electron that was removed from the molecular acts as a `flash’ that illuminates the molecule. Measuring the scattered electron is analogous to measuring the scattered flash with the camera. These methods offer unprecedented temporal resolution that will help us understand electronic motions with molecules. In addition to controlling and probing molecules with strong laser fields, I am interested in understanding a relatively new process that occurs when strong laser fields propagate through air. Research groups around the world have discovered that, when focusing high intensity lasers into air, the nitrogen molecules can sometimes act as a new lasing medium for a second delay weak light pulse. Effectively, energy from the first laser pulse is deposited in the nitrogen molecules, and this deposited energy can be used to amplify a weaker second light pulse. The details of exactly how the energy from the first laser pulse is deposited into the nitrogen molecules is not currently well understood, and my research aims to uncover the underlying mechanism. Understanding the underlying mechanism could lead to opportunities to optimize this process for remote sensing and standoff detection applications.